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Chen Zhixi,Chen Mian,Jin Yan,Huang Rongzun,
,陈 勉,金 衍,黄荣樽

岩石力学与工程学报 , 1997,
Abstract: Fracture toughness is a very important parameter for studying the geometry of hydraulic fractures. In this paper, a simple hydraulic fracturing technique is proposed for determining the fracture toughness of rock, which consists of fracturing prenotched thick wall cylinders with internal hydraulic pressure. A preliminary set of experiments has been performed on sandstone and shale. The mechanism of hydraulic fracturing is discussed by analyzing the fracture surface and acoustic emission activity.
Laboratory Analysis of Acoustic Emission Associated with the Hydraulic Fracturing of Sandstone Samples. The Problem of Fracture Location étude au laboratoire de l'émission acoustique associée à la fracturation hydraulique d'échantillons de grès. Le problème de la localisation de la fracture  [cached]
Deflandre J. P.
Oil & Gas Science and Technology , 2006, DOI: 10.2516/ogst:1989037
Abstract: Acoustic emission associated with the hydraulic fracturing of sandstone samples (dry or saturated) was investigated in the laboratory. The emission sources were located by triangulation from the differences in arrival time of the compressional wave at four sensors. On this experimental scale, the attenuation and dispersion factors, and the anisotropic character of the medium influence the choice of the method for measuring Delta t. For the same reason, the time measurements must be corrected for instrumentation effects. The velocity anisotropy of the medium is also taken into account for a simple geometric representation (ellipsoid). A comparison of the location results with the survey of the fracture after the test shows that the emission sources are located in the fracture plane. The tests also reveal a close correlation between acoustic activity and fracture behavior. The initiation and propagation of the fracture are accompanied by few events only, whereas the closure is characterized by very strong acoustic activity. Two types of event were observed, and those corresponding to the propagation of the fracture appear to confirm a tensile fracture mode. L'émission acoustique associée à la fracturation hydraulique d'échantillons de grès (secs ou saturés) a été étudiée au laboratoire. Les sources d'émission sont localisées par triangulation à partir des différences de temps d'arrivée de l'onde de compression sur quatre capteurs. A cette échelle expérimentale, les phénomènes d'atténuation et de dispersion ainsi que le caractère anisotrope du milieu influent sur le choix de la méthode de mesure des Delta t. Pour cette même raison, les mesures de temps doivent être corrigées des effets de l'instrumentation. L'anisotropie de vitesse du milieu est également prise en compte dans le cas d'une représentation géométrique simple (ellipso de). La comparaison des résultats de la localisation avec le relevé de la fracture après l'essai montre que les sources d'émission se situent dans le plan de fracture. Les essais font également appara tre une forte corrélation entre l'activité acoustique et le comportement de la fracture. La création et la propagation de la fracture sont accompagnées de quelques événements seulement, alors que la fermeture se caractérise par une activité acoustique très importante. Deux types d'événements ont été observés, ceux qui correspondent à la propagation de la fracture semblent confirmer un mode de rupture en traction.
Hydraulic Fracturing: Paving the Way for a Sustainable Future?  [PDF]
Jiangang Chen,Mohammed H. Al-Wadei,Rebekah C. M. Kennedy,Paul D. Terry
Journal of Environmental and Public Health , 2014, DOI: 10.1155/2014/656824
Abstract: With the introduction of hydraulic fracturing technology, the United States has become the largest natural gas producer in the world with a substantial portion of the production coming from shale plays. In this review, we examined current hydraulic fracturing literature including associated wastewater management on quantity and quality of groundwater. We conclude that proper documentation/reporting systems for wastewater discharge and spills need to be enforced at the federal, state, and industrial level. Furthermore, Underground Injection Control (UIC) requirements under SDWA should be extended to hydraulic fracturing operations regardless if diesel fuel is used as a fracturing fluid or not. One of the biggest barriers that hinder the advancement of our knowledge on the hydraulic fracturing process is the lack of transparency of chemicals used in the practice. Federal laws mandating hydraulic companies to disclose fracturing fluid composition and concentration not only to federal and state regulatory agencies but also to health care professionals would encourage this practice. The full disclosure of fracturing chemicals will allow future research to fill knowledge gaps for a better understanding of the impacts of hydraulic fracturing on human health and the environment. 1. Introduction The United States struggles with increasing carbon emissions due to the use of high-carbon energy sources such as petroleum and coal, which together provide the largest portion of primary energy consumption in the country [1]. Energy-related activities have been the primary source of domestic anthropogenic greenhouse gas (GHG) emissions which contributes to the widespread climate-related stress on water resources, livestock, ecosystems, and human health [2]. This appreciation therefore highlights the link between our primary future energy source(s) and future climate change and impacts. Solar, wind, biomass waste, and geothermal and hydroelectric energy have long been recognized as renewable and sustainable energy resources; currently however, they only comprise 9% of our energy consumption; this is in sharp contrast to the rapid growth of national natural gas market production with a record high of 25,319 billion cubic feet (717 billion cubic meters) in 2012 [3]. In fact, natural gas contributed approximately 27% of the total United States energy consumption and accounted for 40% of industrial and 74% of commercial and residential energy consumption in 2012 [1, 3]. Although the accuracy of GHG emission estimates from natural gas production and usage is still a matter of
Interaction between Injection Points during Hydraulic Fracturing  [PDF]
Kjetil M. D. Hals,Inga Berre
Physics , 2012, DOI: 10.1029/2012WR012265
Abstract: We present a model of the hydraulic fracturing of heterogeneous poroelastic media. The formalism is an effective continuum model that captures the coupled dynamics of the fluid pressure and the fractured rock matrix and models both the tensile and shear failure of the rock. As an application of the formalism, we study the geomechanical stress interaction between two injection points during hydraulic fracturing (hydrofracking) and how this interaction influences the fracturing process. For injection points that are separated by less than a critical correlation length, we find that the fracturing process around each point is strongly correlated with the position of the neighboring point. The magnitude of the correlation length depends on the degree of heterogeneity of the rock and is on the order of 30-45 m for rocks with low permeabilities. In the strongly correlated regime, we predict a novel effective fracture-force that attracts the fractures toward the neighboring injection point.
On equivalence of thinning fluids used for hydraulic fracturing  [PDF]
Alexander Linkov
Physics , 2012,
Abstract: The paper aims to answer the question: if and how non-Newtonian fluids may be compared in their mechanical action when used for hydraulic fracturing? By employing the modified formulation of the PKN problem we obtain its simple analytical solutions in the cases of perfectly plastic and Newtonian fluids. Since the results for shear thinning fluids are intermediate between those for these cases, the obtained equation for the fracture length suggests a criterion of the equivalence of various shear thinning fluids for the problem of hydraulic fractures. We assume fluids equivalent in their hydrofracturing action, when at a reference time they produce fractures of the same length. The equation for the fracture length translates the equivalence in terms of the hydraulic fracture length and treatment time into the equivalence in terms of the properties of a fracturing fluid (behavior and consistency indices). Analysis shows that the influence of the consistency and behavior indices on the fracture length, particle velocity and propagation speed is quite similar when considering the PKN and KGD models despite the models refer to different plain-strain states. It appears that from the mechanical point of view, the differences between thinning fluids are not significant; they may be taken into account when wishing to have some quantity to be greater (less) at small (large) time. We conclude that a choice of a fracturing fluid is to be made mostly from technological and/or economic considerations under the condition that the compared fluids are equivalent in their mechanical effect according to the suggested criterion.
Modellization of hydraulic fracturing of porous materials  [PDF]
F. Tzschichholz,M. Wangen
Physics , 2001,
Abstract: We review microstructural fracture growth models suitable for the study of hydraulic fracture processes in disordered porous materials and present some basic results. It is shown that microstructural models exhibit certain similarities to corresponding theories of continua. These similarities are most easily demonstrated for simple crack geometries, i.e., straight cracks (finite size scalings). However, there exist even scaling relations which are completely independent of the particular employed crack structure. Furthermore it is demonstrated that disorder in cohesional/flow properties can influence the crack growth and the resulting fracture geometry in an essential way.
Advanced acoustic emission analysis of brittle and porous rock fracturing  [cached]
Stanchits S.,Dresen G.
EPJ Web of Conferences , 2010, DOI: 10.1051/epjconf/20100622010
Abstract: Analysis of Acoustic Emission (AE) induced during brittle and porous rock fracturing at variety of loading conditions has been performed. On the base of advanced analysis of AE parameters, ultrasonic velocities and mechanical data we found that regardless of applied loading conditions the process of rock fracture can be separated into two main stages: (A) accumulation of non-correlated cracks localized almost randomly in the whole volume of uniformly stressed rock. (B) Final stage of sample fracturing could be characterized by appearance of AE nucleation site followed by initiation and propagation of the macroscopic fault. Contribution of tensile sources is reduced significantly, shear type and pore collapse type events dominate during propagation of a fracture process zone through the sample regardless of applied loading conditions. In the case of porous rock, nucleation of compaction bands could be clearly identified by the appearance of AE clusters inside the samples. Microstructural analysis of fractured samples shows excellent agreement between location of AE hypocenters and faults or the positions of compaction bands, confirming that advanced AE analysis is a powerful tool for the process of rock fracture investigation.
The Effects of Non-Darcy Flow on Hydraulic Fracturing Optimization Design  [cached]
Xinfang MA
Advances in Petroleum Exploration and Development , 2011, DOI: 10.3968/j.aped.1925543820110101.007
Abstract: In recent years, the petroleum industry has been aware of the potential for non-Darcy flow in propped fracture. In hydraulic fracture stimulation treatments, the effects of non-Darcy flow as one of the most critical factors in reducing the productivity of hydraulically fractured high rate wells have been studied widely with examples of field cases. In the hydraulic fracture design, the non-Darcy flow can have great impact on the reduction of a propped half-length, thus lowering the well’s productive capability. These non-Darcy flow effects in propped fractures have been typically associated with high flow rates in both oil and gas wells. This paper studied the effects of non-Darcy flow in fracture on the hydraulic fracturing design, studied the propped porosity and bottom-hole on hydraulic fracturing design and deliverability of fractured well taking into account non-Darcy flow. Key words: Non-Darcy flow; Hydraulic fracturing; Optimization design; Productive capability
Scaling similarities of multiple fracturing of solid materials  [PDF]
P. G. Kapiris,G. T. Balasis,J. A. Kopanas,G. N. Antonopoulos
Nonlinear Processes in Geophysics (NPG) , 2004,
Abstract: It has recently reported that electromagnetic flashes of low-energy -rays emitted during multi-fracturing on a neutron star, and electromagnetic pulses emitted in the laboratory by a disordered material subjected to an increasing external load, share distinctive statistical properties with earthquakes, such as power-law energy distributions (Cheng et al., 1996; Kossobokov et al., 2000; Rabinovitch et al., 2001; Sornette and Helmstetter, 2002). The neutron starquakes may release strain energies up to erg, while, the fractures in laboratory samples release strain energies approximately a fraction of an erg. An earthquake fault region can build up strain energy up to approximately erg for the strongest earthquakes. Clear sequences of kilohertz-megahertz electromagnetic avalanches have been detected from a few days up to a few hours prior to recent destructive earthquakes in Greece. A question that arises effortlessly is if the pre-seismic electromagnetic fluctuations also share the same statistical properties. Our study justifies a positive answer. Our analysis also reveals 'symptoms' of a transition to the main rupture common with earthquake sequences and acoustic emission pulses observed during laboratory experiments (Maes et al., 1998).
Extreme Velocity Fluctuations below Free Hydraulic Jumps  [PDF]
Raúl Antonio Lopardo
Journal of Engineering , 2013, DOI: 10.1155/2013/678064
Abstract: The internal flow of hydraulic jump is essentially an unsteady flow subjected to macroturbulent random fluctuations, and it was not known enough. Then, for the fluctuating motion interpretation, the experimental research on the associated turbulence must be necessary. The author developed in the past extensive laboratory research for the instantaneous pressure field determination by means of pressure transducers and new introductory experiments on velocity fluctuations by means of the ADV technique. The experimental study of the instantaneous pressure field was based on the knowledge of several statistical parameters of amplitudes and frequencies as functions of the Froude number, but for this paper the maximum instantaneous negative of pressure amplitudes on the floor is considered, in order to estimate the extreme maximum positive velocities near the bottom. A useful relationship between turbulence intensity and the pressure fluctuation coefficient was proposed from ADV velocity fluctuation for low incident Froude numbers. By means of this relationship, the value (instantaneous positive semiamplitude with 0.1% of probability to be surpassed) can be considered for the determination of the turbulent extreme velocity near the bottom, under a free hydraulic jump stilling basin with incident Froude number . 1. Introduction Many researchers have studied hydraulic jump, but most of the works have focused on an integral analysis, and little is known about internal flow and turbulence characteristics. For physical knowledge of the hydraulic jump on a horizontal stilling basin, both the mean flow and the fluctuating motion are needed. The mean flow analysis allows the determination of the general pattern of the flow, such as water levels, the jump length, the macroscopic quantification of energy loss, and the mean pressure field. The internal flow of hydraulic jump is essentially an unsteady flow subjected to macroturbulent random fluctuations, and it was not totally known enough. The author developed an extensive laboratory research for the instantaneous pressure field determination by means of pressure transducers and introductory experiments on velocity fluctuations by means of the ADV technique. Early research on the turbulence characteristics of the hydraulic jump was carried out by Rouse et al. [1] using hot-wires techniques in an air model. Acoustic instruments methods were used in hydraulic jumps of low Froude number by Liu et al. [2]. They used a microacoustic Doppler velocity meter (ADV) and presented data of mean velocity, turbulence intensities, and
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